高塩濃度下におけるスケトウダラ筋原繊維タンパク質のＣａＣｌ２による変性

Abstract

The effect of CaCl2 on denaturation of Alaska pollack myofibrillar protein in the presence of 0.5M NaCl (pH 7.0) was studied. On addition of 50mM CaCl2 at 0°C, specific activity of myofibrillar Ca-ATPase was largely decreased but rate and mode of its thermal inactivation were virtually unchanged. A considerable amount of actin as well as tropomyosin turned to be soluble into low ionic strength medium during treatment with CaCl2. It was found that the CaCl2-induced decrease in Ca-ATPase activity and was suppressed by the addition of 1M sorbitol, and that the thermal inactivation mode of CaCl2-treated myofibrillar Ca-ATPase was simultaneously changed from the slow single first order process to biphasic first order step; a fast early phase followed by a slow phase. Moreover, a decrease in specific activity of myofibrillar Ca-ATPase induced by CaCl2. was mostly recovered on addition of carp native F-actin. These results indicated that when 50mM CaCl2 was mixed with Alaska pollack myofibrils in a medium of 0.5M NaCl (pH 7.0), a considerable portion of myofibrillar protein was presumably dissociated into actin and myosin, and myosin rapidly denatured at an almost equal rate with actin. Addition of sorbitol in the medium suppressed the denaturation of dissociated myosin.